package infra

import (
	"context"
	"fmt"

	"golang.org/x/sync/errgroup"
)

// JobWorkerPool starts n workers concurrently, all sharing the same queue and
// handler. It uses errgroup for structured concurrency and supports graceful
// shutdown via ctx cancellation.
//
// The function blocks until all workers exit. It returns the first non-context
// error encountered, or ctx.Err() if all workers stopped due to cancellation.
//
// Options: WithPollInterval, WithJobTypes (applied to every worker).
func JobWorkerPool(ctx context.Context, q *JobQueue, n int, handler JobHandler, opts ...WorkerOption) error {
	if q == nil {
		return fmt.Errorf("job_worker_pool: queue must not be nil")
	}
	if handler == nil {
		return fmt.Errorf("job_worker_pool: handler must not be nil")
	}
	if n <= 0 {
		return fmt.Errorf("job_worker_pool: n must be > 0, got %d", n)
	}

	g, gctx := errgroup.WithContext(ctx)
	for i := 0; i < n; i++ {
		g.Go(func() error {
			return JobWorker(gctx, q, handler, opts...)
		})
	}
	return g.Wait()
}